Determining the useful life of PPE
Most test procedures and standards for PPE recognise that the protective features may deteriorate with use.
It is vitally important that any item of personal protective equipment (PPE) performs adequately throughout its lifetime. User instructions supplied with the item normally include advice to visually inspect and check for physical damage, but in some cases it is not possible to assess if a product still provides the same level of protection as when new. Examples include high-visibility clothing that may have faded or been contaminated, clothing intended for heat and flame applications where continual washing may have reduced the fire-resistant properties of the fabric and fall protection equipment where webbing or rope may have suffered abrasion damage.
In Europe, EC Directive 89/686 requires all PPE to be supplied with instructions for use which, among other things, need to address the ‘obsolescence deadline’, defined as the date after supply or being put into use on which the PPE becomes incapable of fulfilling its intended use. This means that the manufacturer must provide all information necessary so that the user can determine a reasonable period of obsolescence. In terms of inspection prior to using the PPE, the manufacturer must also provide guidance on how to recognise unacceptable damage or signs of ageing, such as cracks in materials or abrasion to webbing.
Most test procedures and standards for PPE recognise that the protective features may deteriorate with use and include at least one test or requirement in an attempt to assess this degradation. However, the ageing process is a complex issue that depends on many environmental factors, most of which are hard to replicate with a simple and quick laboratory procedure. Typically, heat and flame clothing standards may include a requirement to wash an item of PPE several times before reassessing its burning behaviour characteristics to ensure an acceptable level of protection will remain after cleaning in use. High-visibility garment standards include rechecks on colour after subjecting fabrics to UV light from a high-intensity xenon lamp to assess potential fading under periods of simulated exposure to sunlight.
While these simple tests go some way to demonstrating material behaviour, they do not generally replicate everything a garment will be subjected to during its life, and do not simulate the more complex interactions. For instance, repeated washing of garments is not the same as real-life use, where between washing cycles the garment will be worn – which will subject the fabric and seams to conditions that may involve contamination, flexing, UV radiation and mild abrasion. The service life will also depend on storage conditions between use and the effectiveness of any maintenance.
Other standards, such as those in the fall protection arena, rely on safety factors built into the performance levels which, it can be argued, allow for a certain level of degradation or reduction in strength before the product will no longer work effectively. Again, it is difficult to know what safety factor is acceptable and what level of degradation can occur before the damage is sufficiently visible. With all equipment, the importance of a pre-use inspection by the user cannot be overstressed.
Where items of PPE are relatively low cost and disposable after a short time, concerns about maximising the use of the PPE are less important (as long as the PPE always meets the performance requirements). However, some PPE – such as firefighters’ clothing and equipment – is expensive to replace and, therefore, the lifetime of the product is a significant issue to the employers responsible for its purchase and maintenance.
In these situations, manufacturers need to establish how their products perform under a variety of conditions typically encountered in use to estimate obsolescence. The closer these can be made to simulate user conditions, the more accurately the product life can be determined and the more confident a manufacturer can feel regarding claims made.
SATRA is involved with the certification of many types of PPE and also has extensive test facilities, including equipment to artificially age products. For instance, we have environmental chambers ranging from simple ovens to the more complex devices such as corrosion and ozone cabinets or UV and weathering machines. We also have a wide variety of flexing and cyclic loading machines which can be used to fatigue an item and simulate a predefined period of use, after which we can assess whether it still meets the requirements of a particular standard. SATRA also has considerable experience of conducting wear trials, using our own staff or coordinating assessments involving professional user groups.
We have also carried out a number of projects that have involved testing PPE that has been recalled after a period of service to assess any changes in performance and whether safety standards are still met. This has enabled end user groups to make an informed decision as to whether to replace PPE or continue to use the existing products.
SATRA's Essential Guide to PPE is available at www.satrappeguide.com
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